/*
 * Copyright (C) 2006 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.io;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtIncompatible;

import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.Writer;
import javax.annotation.CheckForNull;

/**
 * Writer that places all output on an {@link Appendable} target. If the target is {@link Flushable}
 * or {@link Closeable}, flush()es and close()s will also be delegated to the target.
 *
 * @author Alan Green
 * @author Sebastian Kanthak
 * @since 1.0
 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
class AppendableWriter extends Writer
{
    private final Appendable target;
    private boolean closed;

    /**
     * Creates a new writer that appends everything it writes to {@code target}.
     *
     * @param target target to which to append output
     */
    AppendableWriter(Appendable target)
    {
        this.target = checkNotNull(target);
    }

    /*
     * Abstract methods from Writer
     */

    @Override
    public void write(char[] cbuf, int off, int len) throws IOException
    {
        checkNotClosed();
        // It turns out that creating a new String is usually as fast, or faster
        // than wrapping cbuf in a light-weight CharSequence.
        target.append(new String(cbuf, off, len));
    }

    /*
     * Override a few functions for performance reasons to avoid creating unnecessary strings.
     */

    @Override
    public void write(int c) throws IOException
    {
        checkNotClosed();
        target.append((char) c);
    }

    @Override
    public void write(String str) throws IOException
    {
        checkNotNull(str);
        checkNotClosed();
        target.append(str);
    }

    @Override
    public void write(String str, int off, int len) throws IOException
    {
        checkNotNull(str);
        checkNotClosed();
        // tricky: append takes start, end pair...
        target.append(str, off, off + len);
    }

    @Override
    public void flush() throws IOException
    {
        checkNotClosed();
        if (target instanceof Flushable)
        {
            ((Flushable) target).flush();
        }
    }

    @Override
    public void close() throws IOException
    {
        this.closed = true;
        if (target instanceof Closeable)
        {
            ((Closeable) target).close();
        }
    }

    @Override
    public Writer append(char c) throws IOException
    {
        checkNotClosed();
        target.append(c);
        return this;
    }

    @Override
    public Writer append(@CheckForNull CharSequence charSeq) throws IOException
    {
        checkNotClosed();
        target.append(charSeq);
        return this;
    }

    @Override
    public Writer append(@CheckForNull CharSequence charSeq, int start, int end) throws IOException
    {
        checkNotClosed();
        target.append(charSeq, start, end);
        return this;
    }

    private void checkNotClosed() throws IOException
    {
        if (closed)
        {
            throw new IOException("Cannot write to a closed writer.");
        }
    }
}
